1. Field
This disclosure relates generally to digital-to-analog converters (DACs), and more specifically, to techniques and apparatus for calibrating digital-to-analog converter circuits.
2. Related Art
A digital-to-analog converter (DAC) is a device for converting a digital (usually binary) code to an analog signal such as a current, voltage or an electric charge. DACs are widely used components of various electronic systems, such as telephone and other communications systems, radio transceiver systems, audio systems, image processing systems, and the like.
Many DACs are fabricated in an integrated circuit, where variations in semiconductor manufacturing processes can affect the performance of the DAC. For example, over the entire range of digital codes that can be input into the DAC, a step from one code to the next code in one portion or region of the input codes can produce a different output step size in the analog signal due to nonlinearities introduced in the manufacturing process, or due to differences in circuit architecture used to produce an output signal in one code region compared to another. Some DACs may use some circuits to output a signal with a smaller amplitude, and may use other circuits to output signals with larger amplitudes.
Because nonlinearities or other anomolies can be present in DACs, and because such issues can cause problems in the application and use of the analog outputs signals, there is a need for calibration systems and techniques that can improve upon the accuracy and linearity of the output signals of the DAC.